Flat braided ligament or tendon implant device having texturized yarns

ABSTRACT

A surgical repair device having a length to width ratio of greater than one is disclosed. The device comprises a plurality of fibers. The majority of the fibers are in a direction essentially parallel to the device length. 
     The device has an absorbable component comprising a glycolic or lactic acid ester linkage. The remainder of the device, if any, has a non-absorbable component. The device can be used as a flat braid in the repair of a ligament or tendon.

BACKGROUND OF THE INVENTION

This invention relates to an implantable device composed of one or morebio-absorbable polymer(s) or combinations ofbioabsorbable/non-absorbable polymer(s) for the repair or augmentationof connective tissue damaged by disease or injury. The devices shallserve as scaffolds for ingrowth and orientation of new fibrousconnective tissue, (e.g. ligaments, tendons) in both intra-articular andextra-articular sites by maintaining structural stability during initialhealing and then undergoing at least partial gradual absorption toprevent stress shielding and allow newly formed tissue to becomecorrectly oriented and load bearing.

The invention includes several aspects of device design that areintended to provided for simulation of natural tissue functionimmediately after implantation and to support subsequent fibrous tissueingrowth as well as orientation in the direction of natural loading. Thedevices are braided or woven into a flat tape geometry having theplurality of fibers aligned in parallel to form the axial warp. Thephysical/mechanical/chemical properties of all or part of the componentfibers may be enhanced by a number of temperature/time/stresstreatments. One or more adjacent plies of the device are used in surgeryto achieve biomechanical properties approximately equivalent to thehealthy tissue prior to being damaged. A swivel needle attachment systemmay be incorporated to facilitate handling and surgical placement of thedevices. The interfibrillar space, that provides for initial tissueingrowth, occurs as a result of the braiding/weaving process or may beenhanced by means of texturizing the yarns. Gradual bioabsorption, inwhole or in part, provides for additional interfibrillar space to formduring the healing period, and for fibrous tissue orientation to beinduced as load is transferred from the weakened implant to the`neo-ligament` or `neo-tendon`.

The bioabsorbable materials, biocompatible nonabsorbable materials,physical and chemical combinations thereof, and the processes involvedin fabricating them into the implantable devices are all included inthis invention.

Ligaments and tendons are bands or sheets of fibrous connective tissuewhich provide support and stability to the musculoskeletal system.Relief of the pain and/or instability caused by damage to a ligament ortendon is currently achieved by techniques ranging from simple suturingto removal and replacement with other tissue or a permanent syntheticprosthesis. Although no single technique is appropriate for allsituations, it is generally preferred to return the tissue to it'shealthy, pre-damaged state as naturally as possible. Furthermore, it ishighly desirable to reduce the need for activity restriction during thehealing period. The permanent retention of implanted foreign materialsis considered undesirable and should be minimized because it may resultin stress shielding and subsequent atrophy of natural tissue, or themigration of the materials to other tissues and/or systems (i.e.lymphatic) may occur.

The state-of-the-art in ligament repair/reconstruction is considered tobe the use of autogenous tissue grafts for augmentation or replacementof the damaged ligament. Portions of the patellar tendon, iliotibialband, semitendinosus tendon, and fascia lata are some of the mostcommonly used autogenous tissue grafts. Due to the undesirability ofhaving to sacrifice one tissue and its associated function, in order torepair another, a number of synthetic, permanent total ligamentprostheses and ligament augmentation implants are being tried in animalsas well as clinically.

Several of the permanent ligament prostheses are fabricated so that theproperties of a single synthetic material characterize the implant'sresponse to in-vivo loading (see e.g., U.S. Pat. Nos. 3,896,500;3,953,896; 3,987,497; 3,988,783; and European Patent Applications Nos.51,954; 106,501; and 126,520, all of which are incorporated herein byreference). Although many of the aforementioned patents include morethan one material in the structure of the body of the prosthesis, asingle material determines the mechanical (tensile) properties while thesecondary components are in the form of coatings, sheaths, etc. toimprove biocompatibility or lubricity. While ligamentous tissue is anatural composite material exhibiting both compliant elasticity and highlongitudinal strength, no single synthetic biocompatible material hasthis combination of properties. As a result, implants such as the oneslisted above have tended to fail in animal or clinical trails either bymaterial fatigue, creep (joint laxity), in-vivo degradation or byunacceptable restriction of joint motion.

A number of multi-component ligament prostheses (see, e.g. U.S. Pat.Nos. 3,797,047; 4,187,558; 4,483,023; and European Patent ApplicationNo. 122,744, all of which are incorporated herein by reference are morebio-mechanically compatible with the elasticity and strengthrequirements of natural ligament function but suffer from othershortcomings. Since they are designed to replace the natural ligament,any reparative tissue that forms at the site of the defect, is almostcompletely shielded from applied loads and therefore tends to resorb.The inevitable chemical and/or physical breakdown of these implantsin-vivo, leads to catastrophic failure and a return to pre-operativeinstability, or worse, because no natural tissue repair has taken place.No ligament prosthesis, tried thus far in animals or humans, has yieldedconsistently acceptable joint stability without the occurrence ofimplant breakdown, synovitis, and/or articular tissue damage during thefirst two years post operatively. The desired minimum post operativeperiod of implant/joint stability is 10 years.

Attempts at a long-term `natural` tissue repair (by augmenting but notreplacing the natural tissue) has been approached by the use of avariety of devices and techniques. The use of a permanent device foraugmentation of an autogenous tissue transplant is described in"Experimental Mechanical and Histologic Evaluation of the KennedyLigament Augmentation Device", G. K. McPherson, Ph.D. et al., ClinicalOrthopedics and Related Research, no. 196, pages 186 to 195, 1985, whichis incorporated herein by reference. While the method of attachmentallows the desired natural tissue repair to occur, the entire syntheticimplant remains in situ; some interfibrillar mechanical breakdown hasrecently been reported, and a chronic foreign body response is observedeven at 2 years following implantation. A biologically mechanicallydegradable augmentation device consisting of polyglycolic acid (hereinabbreviated as PGA)--coated carbon fibers (U.S. Pat. No. 4,411,027) orpolylactic acid (herein abbreviated as PLA)--coated carbon fibers (U.S.Pat. No. 4,329,743) has also met with limited success in obtaining a`natural` tissue ligament repair. Both of these patents are incorporatedby reference. However, even though the polymer coating protects thebrittle carbon fibers intra-operatively and is then safely absorbed bythe body, the gross modulus and elasticity mis-match between the carbonfibers and the new ligamentous tissue that infiltrates the implant,results in fragmentation of the carbon fibers. This mechanical breakdownof the carbon fibers does serve to transfer load to the new tissue asdesired, but serious concerns persist regarding the eventual dispositionof the carbon fiber fragments. Finally, as described in "Acute AnteriorCruciate Ligament Injury and Repair Reinforced with a BiodegradableIntraarticular Ligament", H. E. Cabuad, M. D. et al., The AmericanJournal of Sports Medicine, vol. 10, pages 259 to 265, 1982; and "APartially Biodegradable Material Device for Repair and Reconstruction ofInjured Tendons: Experimental Studies", W. G. Rodkey, D.V.M. et al.,AAOS Meeting, 1985, both of which are incorporated herein by reference,and the comparative examples A to F herein, biodegradable implantsconsisting of PGA and polyester (specifically Dacron™) have been triedas repair/augmentation devices for obtaining `natural` ligament andtendon healing. The results of this work indicate that PGA does notretain its properties long enough, in-vivo, and that any tissue thatdoes infiltrate the permanent polyester fiber component does not achieveadequate strength or joint stability due to lack of tissue orientationand excessive ligament/tendon lengthening. The relatively short strengthretention period of PGA, will apparently not allow the elimination ofjoint immobilization that is currently necessary following ligamentrepair or reconstruction.

The surgical repair device of this invention has functional advantagesover the implant device described in European patent (hereafter EP)Application No. 122,744. For example, this invention can utilizeabsorbable fibers in the axial (lengthwise) direction. The majority ofabsorbable fibers in the axial direction enhances or essentiallyguarantees the transfer of the connective tissue stress from the deviceto the ingrowing collagen fibers. In summary, with the majority offibers being in the axial direction and with these fibers being at leastabout 80% absorbable fibers, there appears to be more tissue ingrowthand better oriented collagen fibers.

This invention is useful as a temporary or augmentation device. In thisutility, it seems to match as closely as possible the biologicalproperties of a connective tissue until ingrown collagen fibers canreplace the majority of fibers (preferably having an absorbablecomponent comprising at least about 80 percent) in the axial direction.The advantage of this invention, e.g. over the implant device disclosedin EP Application No. 122,744, is that it appears to provide a surgicalrepair device (specifically for connective tissue, and more specificallyfor ligament or tendon repair) that will have the correct stress relatedproperties to act as a connective tissue (until living tissue canreplace the device). This is accomplished by the ingrown collagen fibersreplacing the absorbable fibers in the axial direction. The use ofnonabsorbable fibers is as a support or backbone for the absorbablefibers.

This invention has superior and unexpected structural properties overthose disclosed in the prior art, specifically EP Application No.122,744. For example, the majority of the fibers in this invention, thatis 50 percent or more, are in the axial (lengthwise) direction.Preferably, 80 to 95 percent are in the axial direction. Thisapproximately twofold increase of fibers in the axial (lengthwise)direction (over the axial direction fibers in EP Application No.122,744) is at least one of if not the primary reason for obtaining thefunctional advantages discussed above.

The surgical repair device of this invention has other advantages overthe prior art. For example, the thickness of the device is smaller thanthe known prior art devices. This is because the majority of the fibersare in the axial direction. The smaller thickness allows this device tobe useful in more constricted connective tissue repair procedures. Also,as a general statement, the smaller the thickness or width of the repairdevice, the greater is its utility as a temporary or augmentation devicebecause tissue ingrowth is facilitated. Conversely, the larger thethickness or width of the device, the more it is used as replacement(that is, as a permanent implant) rather than a temporary device.

It is, therefore, the object of this invention to provide sterile,surgically implantable devices, means for surgical placement/attachment,and fabrication processes that are uniquely suited for providing themost advantageous connective tissue (i.e. ligament, tendon, etc.)repair. These implants resolve the apparent disadvantages of the devicesdescribed above by: 1. providing adequate strength and stiffnessimmediately post-operatively to minimize or eliminate the need forimmobilization; 2. facilitating the ingrowth of vascularized cellulartissue by reason of the open flat tape configuration; 3. supporting theproper orientation of collagen fibers formed within and around theimplant through the predominantly axial alignment of the component yarnsand the gradual transfer of applied loads from the biodegradable yarnsto the newly formed tissue; 4. providing a longer lasting bioabsorbablematerial to permit adequate time for new tissue ingrowth orrevascularization of autogenous tissue grafts or allografts; 5.providing a complaint, elastic, permanent component to protect tissuesfrom over-load, without stress-shielding, for a longer term thanprovided by the bioabsorbable materials, in those applications (i.e.some intraarticular ligament reconstructions) where healing occurs moreslowly; and 6. avoiding the use of materials which fragment and poserisks of migration to adjacent tissues.

The object of this invention comprises bioabsorbable or combinedbioabsorbable/biocompatible polymers fabricated into an elongatedtextile structure having means for surgical placement/attachment at oneor both ends for the purpose of repair, augmentation or replacement ofdamaged connective tissues, such as ligaments and tendons.

SUMMARY OF THE INVENTION

A surgical repair device having a length to width ratio of greater thanone has been invented. The device comprises a plurality of fibers. Themajority of the fibers are in a direction essentially parallel to thedevice length.

The device has an absorbable component comprising from about 10 to 100percent of polymer having a glycolic or lactic acid ester linkage. Theremainder of the device, if any, has a nonabsorbable component.

In one embodiment of the device, the absorbable polymer is a copolymerhaving a glycolic acid ester linkage. In a specific embodiment, thecopolymer comprises glycolic acid ester and trimethylene carbonatelinkages.

A connective tissue repair device having a length to width ratio ofgreater than one has also been invented. The device comprises aplurality of fibers. The majority of the fibers are in a directionessentially parallel to the device length. The device has an absorbablecomponent comprising from about 10 to 100 percent of a copolymer. Thecopolymer has glycolic acid ester and up to about 50 percent by weightof trimethylene carbonate linkages. The remainder of the device, if any,has a nonabsorbable component.

Embodiments of the repair device include a knitted, woven, braided andflat braided device. In one embodiment, the longitudinally orientedmajority of the fibers comprises about 80 to 95 percent. In a specificembodiment, the longitudinally oriented majority of the fibers comprisesabout 90 percent.

In another embodiment, the device has an absorbable component comprisingat least about 80 percent. In a specific embodiment, the device has anonabsorbable component selected from the group consisting of a poly(C₂-C₁₀ alkylene terephthalate), poly(C₂ -C₁₀ alkylene), polyamide,polyurethane and polyether-ester block copolymer. In a more specificembodiment, the device consists of poly(ethylene terephthalate) orpoly(butylene terephthalate) as the poly(C₂ -C₁₀ alkyleneterephthalate), and a polybutester as the polyether-ester blockcopolymer. In a most specific embodiment, the device consists of Hytrel®as the polybutester.

A polybutester can be defined as a polytetramethylene glycol, polymerwith terephthalic acid and 1, 4-butanediol. See, e.g., the definition ofpolybutester in USAN and the USP dictionary of drug names, U.S.Pharmacopeial Convention, Inc., Md. 20852 U.S.A., 1985.

Hytrel® is a trademark of E. I. du Pont de Nemours & Co., Wilmington,Del. U.S.A. for a class of polymers having the following genericformula: ##STR1##

The values for a, x and y are known from the prior art, e.g. asdisclosed in "Thermoplastic Copolyester Elastomers: New Polymers ForSpecific End-Use Applications", M. Brown, Rubber Industry 9 102-106(1978), and the references (footnote numbers 1b, 1c, 1d, 2 and 3) citedtherein; Encyclopedia of Polymer Science and Technology, Supplement, 2485-510, see particularly pages 486 to 493, Interscience N.Y. 1977; andU.S. Pat. No. 4,314,561 issued Feb. 9, 1982. All of this prior art isincorporated herein by reference. A specific embodiment of Hytrel® whichis useful in this invention is a grade of Hytrel® having a 72 durometerD. hardness. The polymer in the NOVAFIL® (American Cyanamid Company,N.J., U.S.A.) surgical suture contains Hytrel®.

A flat braided ligament or tendon implant device having a length towidth ratio of greater than one has been invented. The device comprisesa plurality of fibers. The majority of the fibers are in a directionessentially parallel to the implant length. The braid has about 5 to 100carrier and up to about 50 warp yarns.

The implant has an absorbable component comprising from about 10 to 100percent of a copolymer. The copolymer has glycolic acid ester and fromabout 20 to 40 percent by weight of trimethylene carbonate linkages. Theremainder of the implant, if any, has a nonabsorbable component.

In one embodiment of the implant, the braid has about 13 carrier andabout 6 warp yarns. In a specific embodiment, the implant consists ofabout 100 percent of the absorbable component. In a more specificembodiment, the carrier yarns consist of about 100 percent of theabsorbable component and the warp yarns comprise about 80 percent of theabsorbable component. In a most specific embodiment, the nonabsorbablecomponent in the warp yarns is selected from the group consisting of apoly(ethylene terephthalate) and polyether-ester block copolymer.

In other embodiments of the implant, the yarns are texturized or heattreated. In a further embodiment of the implant, the braid is heattreated.

The bioabsorbable filaments may be comprised of man-made polymersincluding glycolide-trimethylene carbonate (GTMC), polyglycolic acid,polydioxanone, poly(L-Lactic) acid, poly(DL-Lactic) acid and copolymersor physical combinations of the components of these polymers. Naturalbioabsorbable polymers such as regenerated collagen or surgical gut mayalso be used. The biocompatible (nonabsorbable) components includepoly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT),polyether-ester multi-block copolymers, polypropylene, highstrength/modulus polyethylene, polyamide (including polyaramid), orpolyether type polyurethanes. Once spun into filaments, the propertiesof the above materials may be improved for this application by varioustemperature/time/stress treatments.

The device shall be braided, woven or knitted so that the structure hasthe desired strength and stiffness in the primary (axial) loadingdirection. It also has adequate interfibrillar space and minimizedthickness to promote the ingrowth of tissue. The end(s) of the devicemay be compressed inside biocompatible metal sleeve(s) to which swivelend-caps(s) and surgical needle(s) are attached in such a way as topermit rotation of the needle(s) about the longitudinal axis of thedevice.

In use, an appropriate number of plies of the device are implanted tomatch the biomechanical properties of the tissue being repaired. Thispermits an early return to normal function post-operatively. As theligament or tendon begins to heal, the implant continues to bear anyapplied loads and tissue ingrowth commences. The mechanical propertiesof the bioabsorbable component(s) of the implant then slowly decay topermit a gradual transfer of loads to the ingrown fibrous tissue,stimulating it to orient along the loading direction. Additionalingrowth continues into the space provided by the absorbed components ofthe implant. This process continues until the bioabsorbable component(s)are completely absorbed and only the newly formed tissue remains, or thebicompatible (nonabsorbable) component(s) are left in situ to providelong-term augmentation of the newly formed tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of the device described as the preferredembodiment, except that two different possible ends are shown.

FIG. 2 is an enlarged view of the flat surface of the preferredembodiment showing the braided construction in greater detail.

FIG. 3 is an anterior view of a knee showing the device as positionedfor repair of the excised patellar ligament in animal (canine) studies.

FIG. 4 is an anterior view of a knee showing the device as positionedfor augmentation of the medial third of the patellar ligament in anAnterior Cruciate Ligament reconstruction.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In preferred embodiments the elongated textile structure 1 of theimplant comprises a flat braid having primarily axial (quoit) yarns 2 ofan absorbable polymer such as GTMC. The number and denier of quoit andsleeve yarns are varied to provide devices having a range of propertiesthat are biomechanically compatible with any likely implant site. Swivelend cap(s) 3 and surgical needle(s) 4 may be attached at the end(s) ofthe device to facilitate placement and attachment.

The procedures described below are followed when preparing flat braidsto be used as artificial ligaments/tendons starting from the appropriateyarns. To begin, the proper denier yarns for the specific braidconstruction are required. This example describes a typical constructiondesigned to fit a particular animal model--repair/replacement of thecanine patellar ligament (FIG. 3). An application that had a tensilestrength/stiffness requirement three times higher than that described inthe example would require three times as much yarn. This could beaccomplished by simply tripling the final total braid denier, either byincreasing the yarn denier or increasing the number of sleeve and quoit(stuffer yarns) or both.

To produce a braid for canine patellar ligament repair (FIG. 3), a finalbraid denier between 13,000 and 24,000 is targeted. In the preferredconstruction, approximately 90% of the fiber is contained in theparallel quoit or warp yarns 2.

The sleeve yarns 5, which consist completely of absorbable material, aregenerally about 130 denier. On transfer they are given a nominal 1.4turn per inch (TPI) `Z` or `S` twist before further processing. Thisfacilitates handling and minimizes fiber breakage. It is to beunderstood that the term "carrier" yarns, as disclosed for example inthe above "SUMMARY OF THE INVENTION", is synonymous with the term"sleeve" yarns.

The quoit (stuffer or warp) yarns can be 100% absorbable or they maycontain a nonabsorbable component. They are much heavier than thesleeve, generally ranging from 2100 to 2700 denier. This necessitatestwo passes on a six position ply twister. A 130 denier yarn wouldnormally be 5-plied 2.8 TPI `S` or `Z`, then 4 ends of the 5-ply yarnwould be twisted 1.4 TPI in the reverse direction. This would result ina final quoit yarn denier of 2600, mechanically balanced from thereverse twist operation (no tendency to twist or unravel).

Nonabsorbable components 6, if included, are blended into the quoityarns during the 1st ply twisting operation. For instance, aMAXON™/NOVAFIL® (American Cyanamid Co., N.J. 07470 U.S.A.) bicomponentyarn consisting of 18-22% nonabsorbable fiber would be made by running 1yarn of 130 denier NOVAFIL® with 4 yarns of 130 denier MAXON™ in the5-ply operation. The preparation and polymeric composition of MAXON® isdisclosed in U.S. Pat. Nos. 4,429,080; 4,300,565 and 4,243,775; thepreparation and polymeric composition of NOVAFIL® is disclosed in U.S.Pat. Nos. 4,314,561; 4,246,904; and 4,224,946. All of these patents areincorporated herein by reference. The exact proportion of NOVAFIL® isdetermined by the yarn deniers involved and the proportion of quoityarns in the braid construction.

An important processing step for some absorbable yarns is post treatment(a vacuum annealing step which upgrades the implant tensile values).Generally speaking, for a construction that is to be 100% absorbable,the yarns are post treated after ply twisting; for anabsorbable/nonabsorbable biocomponent construction, the absorbable yarnsare post treated prior to ply twisting. There is another option and thatis to post treat the final braid, providing it does not have adeleterious effect on a nonabsorbable component.

After ply twisting and post treatment, the yarns are ready for braiding.The best results to date are obtained with a construction that is madeon a 13 carrier flat braider, which has 6 quoit yarn feeds. About 90% ofthe construction is composed of the heavy parallel quoit yarns heldloosely together by the sleeve yarns at 12.3 picks (yarn cross-overpoints) to the inch.

After braiding, the ligament is ready for further processing. It is cutto length and sleeved on both ends with a 1/4" aluminum or silversleeve. A stainless steel over cap 3 with a small metal swivel pin 7 isthen attached.

The end capped ligaments are now ultrasonically washed in xylol toremove any residual finishing oils (6 min residence in each of 4 baths).After the implants are air dried, appropriate needles 4 are attached tothe metal pins to allow the implant to swivel in use.

They are then packaged in preformed plastic trays with a lid and in openaluminum foil laminate envelopes. They are sterilized in an EthyleneOxide cycle which includes an elevated temperature vacuum drying step.The foil laminate envelopes containing the dry ligaments are thenheat-sealed in an asceptic glove box hood fed by dry air. Any interimstorage needed between vacuum drying and heat sealing is carried out inan asceptic sealed box fed, again, by dry air.

Devices, as described above, may be surgically implanted to bridge adefect in a ligament, as a replacement for an excised damaged ligament(FIG. 3) or as an augmentation (FIG. 4) for autogenous tissue graft (orallograft) ligament reconstruction. In those surgical proceduresrequiring passage through and/or attachment to soft tissue 9, implantshaving the end-cap 3 and swivel needle(s) 4 at the end(s) would be used.For those applications in which the implant only needs to be passedthrough an open joint space 10 or through pre-drilled tunnels in bone11, the swivel needles would not be required. Implants provided for suchprocedures may instead have either: (a) melt-fused ends to preventfraying, or (b) ends stiffened by surrounding tubes 8 that aremelt-fused or heat-shrunk onto the material of the device itself.

The invention can be described by the following examples.

EXAMPLE 1

The implant consists of 100% MAXON™ yarns in a 13 carrier flat braidconstruction. It was made from 100 denier/8 fil MAXON™ yarns that werepost treated prior to twisting. Both sleeve and quoit yarns were twistedat 10 TPI to retain yarn integrity. The sleeve yarns consisted of 13carriers holding 200 denier yarns made by 2-plying the 100 denier yarns.The 6 quoit or stuffer yarns were made by a double pass (6 yarns over 6yarns) on the ply twister to form a 3600 denier yarn. The final braiddenier was 24,200 with 89.3% of the fibers contained in the quoits.Picks/inch were calculated at 12.3.

The braid was then forwarded to an outside vendor to be cut to lengthand end capped. On return, the implants were washed ultrasonically inxylol, dried, needled and packaged. In this instance, packagingconsisted of a 1 mil aluminum foil inner envelope, dry sealed after ETOsterilization and vacuum drying. Inner envelopes were then overwrappedin a TYVEK™ (E.I. du Pont de Nemours & Co., Del. 19898 U.S.A.) packageprior to a 2nd ETO sterilization cycle.

Straight pull tensile strengths averaged at 203 lbs equivalent to 3.8grams/denier with an extension to break of 33.4%. Hydrolytic strengthdata indicated that the device was viable and samples were implanted in10 month or older beagle dogs replacing the canine patellar ligament.Sacrifices occurred at 2, 4 and 6 months. Histological examinationindicated 50-90% infiltration of the device by cellular tissue and somecollagen fiber at 2 months, and well organized collagen replacing theabsorbed MAXON™ at 6 months. Some displacement of the patella wasevident at 2 and 4 months, but 6 month x-ray data approximated thenon-operated controls. `Neo-ligament` cross sectional area at the 2month interval was approximately 2 to 3 times that seen on thenon-operated controls. The size of the tissue mass gradually decreasedat subsequent post-operative evaluation periods. Final tensile strengthsof excised ligaments ranged from approximately 180 lb. at 2 months, toapproximately 250 lb. at 4 and 6 months, with extensions at break of 7.9to 9.2 mm which are in the range of the unoperated controls.

EXAMPLE 2

This implant also consists of 100% MAXON™ in a flat braid construction.However, the source yarns were heat stretched at 32% prior to braidingand post treated after braiding. The construction itself consisted of1-124d sleeve yarns twisted to 2.2 TPI `S` and 6-2232d quoit yarns plytwisted as follows: first 3 yarns at 2.2 TPI `Z` which were then reversetwisted--6 yarns at 1.1 TPI `S`. The total final denier was 15,000 with89.3% comprised of quoit yarns. This construction also had 12.3Picks/inch.

This braid has a 148 lb breaking strength (equivalent to 3.94grams/denier) with an extension at break of 26.2%. Hydrolytic dataindicated the material was viable as an implant. Sterile devices of thistype were prepared as in Example 1.

EXAMPLE 3

This implant was a MAXON™/DACRON® bicomponent in an approximately 80/20blend. DACRON® is a trademark of E. I. du pont de Nemours & Co.,Delaware 19898 U.S.A, for a synthetic poly(ethylene terephthalate)fiber. Both components had been heat stretched at 18.5-20% prior to plytwisting. To make the quoit yarns, four yarns of 120d MAXON™ weretwisted at 1.4 TPI `Z` and then combined with 1 yarn of 127d DACRON®(also twisted at 1.4 TPI `Z`) in a ply twisting operation at 2.8 TPI`S`. Four of these bicomponent yarns were then reverse twisted at 1.4TPI `Z` for a total denier of 2428. The sleeve yarn was simply 120dMAXON™ twisted to 9.1 TPI `Z`.

The flat braid was made on a 13 carrier machine with 6 quoit yarns at a12.3 pick. Total denier was 16,128 with 90.3% of the total constructioncombined in the quoits. 18.9% of the total construction consisted of thenonabsorbable (DACRON®) component.

This sample broke at 140 lbs (equivalent to 3.94 grams/denier) with a24.2% breaking elongation. Hydrolytic data indicated the sample wasviable. Samples were prepared as in Example 1, and implanted in 10 monthor older beagle dogs replacing the canine patellar ligament.Histological evaluation of the repaired ligament at 2 months indicatedthe ingrowth of cellular tissue to be localized near the implantperiphery. At subsequent post-operative intervals, collagen was observedas an oriented fibrous sheath surrounding the remaining Dacron® yarnswith minimal tissue infiltration or vascularization noted. However, thecross-sectional area, as well as the length of the neo-ligaments weresubstantially equivalent to those obtained with the device of Example 1.Average tensile strengths of the repaired ligaments at the 2, 4 and 6month post-operative evaluation periods also ranged from approximately180 lb. to 250 lb. The extensions at break for ligaments repaired withthese particular devices were between 8 and 16 mm; generally greaterthan the unoperated controls.

EXAMPLE 4

This construction utilized heat stretched MAXON™ combined with NOVAFIL®in an 80/20 combination. The sleeve yarn was simply 120d MAXON™ twistedat 9.1 TPI `Z`. The quoit yarns consisted of 2 yarns of 68d NOVAFIL®that had previously been ply twisted at 1.4 TPI `Z` combined with 4yarns of MAXON™ twisted to 1.1 TPI `Z` prior to heat stretching at 20%.These yarns were ply twisted at 2.8 TPI `S`. Four of these bicomponentyarns (of about 616 denier) were then reverse twisted at 1.4 TPI `Z` togive a quoit yarn of 2464 denier.

These yarns were braided on a 13 carrier flat braider with 6 quoit endsat 12.3 picks/inch. Final braid denier was 16,344, of which 90.5% wascontained in the quoits. Approximately 22.1% of the total constructionwas the nonabsorbable component-NOVAFIL®.

The resulting ligament broke at 155 lbs (equivalent to 4.31grams/denier). The extension at break was 27.4%. Hydrolytic testsindicated that this design was a viable one. After further processing,as in Example 1, devices of this type were implanted in 10 month orolder beagle dogs replacing the patellar ligament. Compared to therepairs made with the devices described in Examples 1 and 3, theseimplants appeared to yield the best histological results. Approximately70-90% of each of the implants had been infiltrated with well organized,vascularized, cellular tissue and some collagen fibers within 2 months.Results improved with time, so that at six months the non-absorbableNOVAFIL® yarns served as a scaffold that was completely infiltrated withwell vascularized, axially oriented collagen fibers. The `neo-ligament`cross-sectional area and length followed the same trends as in Examples1 and 3. Tensile strengths gradually increased from approximately 180lb. at 2 months to about 250 lb. at 6 months; well within the range ofunoperated control strengths which averaged 220 lb. Theextension-at-break remained fairly constant at 11-12 mm which, whilegenerally greater than the unoperated controls was intermediate to theresults noted in Examples 1 and 3.

Examples 5 to 10 were part of an experimental study designed todetermine the effect of heat stretching and post treatment on MAXON™.The net conclusion was that post treatment served to upgrade implantproperties; heat stretching by itself or in combination with posttreatment did not markedly improve MAXON™ implant properties aftersterilization.

EXAMPLE 5

This construction is also 100% MAXON™ in a flat braid construction. Theyarns were not heat stretched before braiding. The sleeve yarnsconsisted of 130d MAXON™ twisted to 1.4 TPI `S`. The quoit consisted of5 yarns of 130d MAXON™ twisted to 2.8 TPI `Z`. Four yarns of this 5 plyconstruction were then twisted to 1.4 TPI `S` for a total denier of2600.

The above yarns were then braided on a 13 carrier braider with 6 quoitends set at a 12.3 pick. The final construction came to 17,694 denier,of which 90.2% were quoit ends.

After sterilization this construction measured 19,134 denier. It had a138 lb breaking strength (equivalent to 3.27 grams/denier) and anextension at break of 54.2%.

EXAMPLE 6

The same as Example 5 except that the yarns used were post treatedbefore braiding.

The final denier was 17,550 which changed to 18,288 after sterilization.The sterile devices had a breaking strength of 126 lbs (3.13grams/denier) with an extension at break of 38.1%.

EXAMPLE 7

The same as Example 5 except that the braid itself was post treated.

The final denier was 17,811 which changed to 18,414 after sterilization.Strength to break was 145 lbs (3.57 grams/denier) with an extension atbreak of 39.3%.

EXAMPLE 8

The same as Example 5 except that the ply twisted yarn was heatstretched at 26% before braiding. Material was not post treated eitheras a yarn or braid.

The final denier was 16,497 which changed to 19,332 after sterilization.Strength to break was 121 lbs (2.84 grams/denier) with an extension atbreak of 44%.

EXAMPLE 9

Same as Example 8 except that this yarn was post treated after heatstretching.

The final denier was 15,786 after braiding. On sterilization thischanged to 18,034. The strength to break of the sterile devices was 135lbs (3.41 grams/denier) with an extension at break of 34.2%.

EXAMPLE 10

Same as Example 8 except that the braid itself was post treated.

The final denier was 16,362 after post treating; 17,392 aftersterilization. The strength to break of the sterile implants was 150 lbs(3.90 grams/denier) with an extension at break of 34.6%.

EXAMPLE 11

This embodiment consisted of 100% MAXON™ in a flat braid construction.It differs from constructions described in previous examples in that itwas airjet texturized prior to the initial twisting steps. The sleeveyarn consisted of 149d texturized MAXON™. This was made by overfeeding 2yarns of 66 denier MAXON™ into the airjet chamber-one by 15% and theother by 8%. This material was then twisted to 1.4 TPI `Z`. The quoityarn started with 219 denier texturized MAXON™. This was made byoverfeeding 1 end of 66d MAXON™ at 15% into the airjet along with 1 endof 130d MAXON™ at 8%. The 219 denier yarns were then 3-plied at 2.8 TPI`S`. Four yarns of the 3-ply material were then reverse twisted at 1.4TPI `Z` to give a final denier of 2523.

This material was braided on a 13 carrier flat machine at 12.3 picks perinch. Its final denier measured 17,693 with 88.7% of the construction inthe quoits.

The straight pull to break averaged 130 lbs (3.3 gms per denier) with anextension at break of 26.7%. As expected, its surface appearanceresembled that made of yarns spun from a natural, staple fiber such ascotton or wool. Optically, the braid could be characterized as having aloose, single fil looped appearance. Subsequent processing of the braidis as described above under the heading `Description of the PreferredEmbodiment`.

EXAMPLE 12

This design is identical to Example 11 except that in the initial3-plying of the quoit yarns one end of a 245 denier MAXON™/NOVAFIL®texturized bicomponent yarn was substituted for one of 219 deniertexturized MAXON™ yarns. This MAXON™/NOVAFIL® bicomponent was made byoverfeeding a 66d MAXON™ yarn at 55% and two 69d NOVAFIL® yarns at 11%into the airjet chamber. The denier of the 12 ply quoit yarn wasmeasured to be 2667d.

This material was braided on a 13 carrier flat machine at a 12.3 pick.Its final denier was 18,467 of which 89.2% was quoit yarn and 19.1% wasthe nonabsorbable NOVAFIL® component.

The final non-sterile ligament had a breaking strength of 122 lbs (3.00grams per denier) and an extension at break of 25.9%. Hydrolytic dataindicates that this will make a viable product with a residual strengthof 29.5 lbs.

Subsequent processing of the braid is as described above under theheading `Description of the Preferred Embodiment`.

EXAMPLE 13

This implant design is identical to Example 11 except that in theinitial 3 plying of the quoit yarns one end of a 226 denier MAXON™/HeatStretched Texturized DACRON® bicomponent yarn was substituted for one ofthe 219 denier MAXON™ yarns. This MAXON™/Heat Stretched DACRON®bicomponent was made by overfeeding a 66 denier MAXON™ yarn at 55% and a127 denier heat stretched DACRON® yarn at 11% into the airjet chamber.The denier of the 12 ply quoit yarn measured 2613.

This material was braided on a 13 carrier flat machine at a 12.3 Pick.Its final non-sterile denier was 18,054, of which 89.0% was quoit yarnand 20.7% was the nonabsorbable heat stretched DACRON® component.

The final non-sterile ligament had a breaking strength of 97 lbs (2.43grams per denier) and an extension at break of 21.7%. Hydrolytic dataindicated it would remain unchanged in strength for 14 days and wouldhave a residual strength of 34.7 lbs.

Subsequent processing of the braid is as described above under theheading `Description of the Preferred Embodiment`.

EXAMPLE 14

This construction consists of 100% MAXON™ in a flat braid construction.It differs from previous constructions in that it is braided on a 21carrier machine.

The sleeve yarn consists of 66 denier MAXON™ yarn twisted to 1.4 TPI`Z`. The 130 denier quoit yarns are first 2-plied at 2.8 TPI `S`--then 5yarns of this 2-ply construction ar TPI `Z`. The final denier of the 10ply quoit yarn is 1300.

The above yarns are then braided on a 21 carrier machine with 10 quoityarns set at a 12 picks/inch. The final construction measures 16,986denier, of which 91.8% is quoit yarn.

Samples are expected to have a non-sterile breaking strength of 124 lbs(equivalent to 3.31 grams per denier) with an extension at break of35.2%.

EXAMPLE 15

This construction consists of 100% MAXON™ in a flat braid construction.It differs from previous constructions in that it is braided on a 15carrier machine.

The sleeve yarn consists of 98 denier MAXON™ twisted to 1.4 TPI `Z`. The130 denier quoit yarns are 5-plied at the same level of twist to give atotal denier of 650. All yarns are post treated after plying.

The above yarns are braided on a 45 carrier machine. Only 15 out of 45available carriers are used for the sleeve yarns. All of the available22 quoit positions are used. The braider is set for a 4.1 pick. Thefinal construction measures 15,770 denier, of which 90.7% is parallelquoit yarn.

Straight pull tensile strength is expected to average approximately 168lbs (4.83 grams/denier) with a 37.2% elongation at break.

EXAMPLE 16

This implant design is similar to Example 15 except that 1 yarn of heatstretched DACRON® is substituted in ply twisting the quoit yarns. Also,all MAXON™ yarns are post treated prior to twisting.

The final braid denier is 15,700, of which 90.7% is parallel quoit yarn.Approximately 18.1% of the total construction is the nonabsorbableDACRON® component.

Straight pull tensile strength is expected to be approximately 127 lbs(3.67 grams/denier) with a breaking elongation of 29.3%. Hydrolytic datafrom similar constructions indicate that this design would make a viableproduct with a residual strength of 29 lbs due to the nonabsorbablecomponent.

EXAMPLE 17

This design consists of 100% MAXON™ in a flat braid construction.Although braided on a 45 carrier machine, it differs from Sample 15 inthat it is 3.3 times heavier.

The sleeve yarns consist of 130 denier MAXON™ twisted to 1.4 TPI `Z`.The 130 denier quoit yarns were first 4-plied to 2.8 TPI `Z`, then four4-ply yarns are reverse plied to 1.4 TPI `S` to give a final quoit yarndenier of 2080. All yarns are post treated after twisting.

The above yarns are then braided on a 45 carrier machine using allavailable carriers for the sleeve and all of the available 22 quoit yarnpositions. The braider is set for a 12.3 pick. The final constructionmeasures 51,610 denier, of which 88.7% is parallel quoit yarn.

Straight pull tensile strength is expected to average 525 lbs (4.61grams/denier) with a breaking elongation of 31.6%.

Although the following examples, and variations thereof, may be suitablefor some soft tissue orthopedic (i.e. tendon) repair/reconstructionapplications, they have been found to be inappropriate as ligamentimplants and therefore not part of this invention. They are disclosedfor their comparative value to Examples 1-to-17, and as a contributionto the state of the art.

COMPARATIVE EXAMPLE A

This construction is a round bicomponent braid consisting of threebraided elements.

a. A subcore which is a blend of 20/80 PGA/Heat Stretched DACRON®. Thissubcore was made on an 8 carrier braider set at 5 picks/inch with eachcarrier containing a 1060 denier bicomponent yarn. The 1060 denier yarnwas made by ply twisting 4 yarns of 210 denier heat stretched DACRON®with 2 yarns of 110 denier DEXON® (American Cyanamid Co., N.J. 07470,U.S.A.) at a low nominal level of twist. The preparation and polymericcomposition of DEXON® is disclosed in U.S. Pat. No. 3,297,033, which isincorporated herein by reference.

b. A core is also a blend of 20/80 PGA/Heat Stretched DACRON®. This wasmade by braiding on a 12 carrier braider set at 5 picks/inch using the 8carrier braid described above as a core. Each of the 12 carrierscontained a 1270 denier bicomponent yarn which was made by ply twisting5 yarns of 210 denier Heat Stretched DACRON® with 2 yarns of 110 denierDEXON® at a low level of twist.

c. The final sleeve was a blend of 60/40 PGA/Heat Stretched DACRON®.This was made by braiding on a 16 carrier braider set at 15 picks perinch using the 12 carrier braid described above as a core. Each of the16 carriers contained a 1510 denier bicomponent yarn which was made byply twisting 3 yarns of 210 denier Heat Stretched DACRON® with 8 yarnsof 110 denier DEXON® at a low level of twist.

All of the above yarns were post treated after ply twisting. This braidbroke at 430 lbs straight pull (equivalent to 4.07 grams/denier) with an18.8% extension at break. Braid denier was calculated to be 47,900.

Intramuscular and subcutaneous implants in canines exhibited little, ifany, tissue ingrowth. Braids were encapsulated by unorganized collagen.This lack of vascularized cellular tissue and oriented collageninfiltration into the implant is considered undesirable for ligamentrepair or reconstruction. It is most probably a combined effect of: 1.the relatively short strength retention period of the PGA (i.e. 28days); and 2. the tight round construction which minimizesimplant-tissue interface area.

COMPARATIVE EXAMPLE B

This construction was basically the same as that in Comparative ExampleA except that the final sleeve was a 50/50 PGA/Heat Stretched DACRON®bicomponent yarn in a finer (more dispersed) blend. This was made on a16 carrier braider set at 15 picks/inch using the 12 carrier braiddescribed in Example A as a core. Each carrier contained a 1320 denierbicomponent yarn made by first ply twisting 1 yarn of 110 denier HeatStretched DACRON® with 1 yarn of 110 denier DEXON®. Six of the 2-plybicomponent yarns were then twisted to make the final 12-ply yarn. Twistlevels were of a low order of magnitude.

The final braid denier was calculated to be 44.8K. The breaking strengthmeasured 385 lbs (equivalent to 3.89 grams/denier) with a breakingelongation of 16.8%. Animal implant data were similar to Example A.

COMPARATIVE EXAMPLE C

This construction was, again, basically the same as in ComparativeExample A except that the final sleeve had a coarser (less dispersed)configuration. It consisted of alternating a 1650 denier DACRON® (HeatStretched) yarn with 1650 denier DEXON® yarn on each of the 16 carriers.

The final breaking strength was 429 lbs (equivalent to 3.88grams/denier). The elongation at break was 17.8%. The final denier wascalculated to be 50,100. Animal implant results were similar to ExampleA.

COMPARATIVE EXAMPLE D

This implant design was 100% DEXON® PGA in a round braid configurationand it consisted of three braided elements:

a. The subcore was made on an 8 carrier braider set at 5 picks/inch.Only 4 out of the eight sleeve carriers were used. The 440 denier yarnwas made by plying four 110 denier yarns at a low number of twists perinch.

b. The core was made on an eight carrier machine also set at 5picks/inch with all eight carriers containing a 550 denier yarn. Theyarn was made by plying five 110 denier yarns at a low level of twist.The 4 carrier braid described above was used as a core.

c. The sleeve was made on a twelve carrier braider set at 15 picks/inchwith all 12 carriers containing a 660 denier yarn. The yarn was made byplying six 110 denier yarns at a low level of twist. The eight carrierbraid described above was used as a core.

The final denier was calculated to be 14,100. Tensile strength measuredto be 134 lbs (equivalent to 4.32 grams/denier). The elongation at breakwas 33.4%.

Implant results

This material was implanted as a replacement for the resected patellarligament of 10 month or older beagle dogs. At 1 and 2 months there wasno histological evidence of tissue ingrowth. Braids were encapsulated byunorganized collagen and were structurally weak. This construction wasabandoned since there was little hope for its use in ligament repair orreplacement applications where ingrowth is desired.

COMPARATIVE EXAMPLE E

This implant design was 100% DEXON® (PGA) in a flat braid configurationand consisted of heavy denier quoit or warp yarns held together by lightdenier sleeve yarns:

a. Each quoit yarn contained 2214 denier DEXON® which was made by plytwisting three--123 denier yarns to give 369 denier yarn and then plytwisting six of these 369 denier yarns at 1.5 TPI `S`.

b. The sleeve yarn contained 110 denier DEXON® yarns which were twistedto 10 TPI `S`.

c. The braid was made on a thirteen carrier braider--each carriercontaining 110 denier sleeve yarn which was braided about the 2214denier warp yarns fed through all six available quoit positions. Thetotal pick count was estimated at 10 per inch.

d. This construction was washed and post treated as a braid.

The total braid denier was approximately 15,100. Tensile strengthmeasured 208 lbs. with a 22.3% elongation-to-break.

Devices of this design were implanted as replacements for the resectedpatellar ligament of 10 month or older beagle dogs in a comparativestudy with devices of Example 1. Histological evaluation at 1 and 2months post-operatively revealed no significant tissue ingrowth ororganization within the PGA implant. This lack of ligament repair wasattributed to the relatively shorter in-vivo property retention periodof the PGA material.

COMPARATIVE EXAMPLE F

This implant design was 100% DEXON® (PGA) in a flat braid configurationand again consisted of heavy denier quoit or warp yarns held together bylight denier sleeve yarns. However, all the yarns were post treated;then air jet texturized prior to twisting and braiding.

a. The quoit (warp) yarn consisted of a 6 ply construction using 357denier texturized DEXON® yarn to give a total 2142 denier yarn. This 357denier yarn was made by entangling 3 ends of 110 denier DEXON® yarn--2yarns with a 24% overfeed and one with a 6% overfeed.

b. The sleeve yarn was made similarly except it was a 152 denier,texturized DEXON® yarn. This was made by entangling 2 yarns of 62 denierDEXON®--one yarn with a 24% overfeed and the other with an 11% overfeed.

c. The braid was made on a thirteen carrier braider, each carriercontaining the 152 denier yarn described in section b above. Thesesleeve yarns were braided about the 2142 denier warp yarns fed throughall six available quoit positions. The total pick count was estimated at12.3 per inch.

The total braid denier was 14,800. Tensile strength measured 152 lbs.with a 23.2% elongation-to-break.

Devices of this construction were evaluated in-vivo as described in theprevious example. Upon sacrifice at 2 months, these implants were foundto have better tissue ingrowth/organization than the non-texturized PGAdevices of the previous example. However, the results achieved withimplants made using the longer lasting GTMC yarns were consistently,significantly improved over those obtained with the devices of thesecomparative examples.

We claim:
 1. A flat braided ligament or tendon implant device having alength to width ratio of greater than one, comprising a plurality offibers, the majority of the fibers being in a direction essentiallyparallel to the implant length, the braid having about 5 to 25 carrierand up to about 10 warp yarns, wherein the yarns are texturized, andsaid implant having an absorbable component comprising from about 10 to100 percent of a copolymer, the copolymer having glycolic acid ester andfrom about 20 to 40 percent by weight of trimethylene carbonatelinkages, and the remainder of said implant, if any, having anonabsorbable component.